22

You are broadly correct. We can divide appliances into three broad categories: Items that run off external low-voltage power supplies: Examples might include laptops (when connected to mains power), printers, etc. These devices depend upon external power supplies (nowadays usually switch-mode power supplies) to convert mains-voltage AC current to DC at the ...


19

Let's look at how much electricity and money can be saved by using solar thermal to heat a cylinder of hot water, rather than by using an electrical resistance heater. Assuming a 100% efficient resistance heater (that's near enough to real values), and ignoring tank losses during the heating period. 180 litres of water is near enough 180kg. The specific ...


19

Of course that depends on the battery, but Lithium Ion batteries were the standard for laptop/cellphone batteries last time I checked. A battery feels most happy being neither too full nor too empty, being not too hot, being not charged/recharged too often. If you don't need the battery, remove it from the battery pack (at about 60%) and store it dry and ...


14

TLDR; cadmium telluride panels have the highest EROI of the mentioned PV panels (around 34.2) EROI estimates vary widely. This is because of differences in the method of calculation, scope of the study, installation location, assumed lifespan of a panel, etc. This also makes it relatively easy to manipulate EROI calculations. Pessimistic The most ...


13

i signed up just so i could make this comment. THelper♦ provided a good link to a DOE report on this topic, which i was researching because my roommate is skeptical about the advantages of efficient bulbs. the report THelper♦ cited has the following bar graph that pretty much answers the question:


13

No. There is no readily available supply of net-positive-energy hydrogen on Earth, where most human power usage takes place. Hydrogen fuel cells may be a useful component of a total energy system but they are not a source of generation capacity. Hydrogen is more like a battery than a supply of energy. Hydrogen can be liberated from water by using energy. ...


12

Someone has done it. A majority of the electricity I buy comes from geothermal energy †. Of course, I live in the Pacific Northwest of North America, which puts me close to a tectonic plate boundary. This presents good conditions for extracting geothermal heat (since the earth's crust is thinner at such boundaries ... making shallower wells productive). ...


12

I highly suggest buying a Kill-a-Watt type device which measure how much energy is used on an outlet. Test each appliance separately, and see which one is really sucking energy in your home and requires unplugging. It's the fastest and easiest solution to test precisely the devices you use. (Note: This is a repeat of my comment, but I'm not getting any ...


12

No. With nothing plugged in there is no circuit, so no current can flow. An exception to this is if the socket or the switch has an indicator light - usually a neon one - that is illuminated when the switch is on. In that case the light will use a (very small) amount of power.


11

Yes, we can. Estimates vary of the losses in long-distance HVDC (high-voltage direct current) transmission, but they're around 3-4% per 1000 km. Now, those operate at far higher voltages than you've mentioned: you wrote of 10 000 V, which is also written as 10 kV. HVDC runs at 100-800 kV, i.e. 10 to 80 times higher (100 000 to 800 000 V). The idea of using ...


10

No, you cannot get more energy out than you put in. No, you cannot invent a perpetual motion machine.


9

The answer you are looking for would be contained in a Life Cycle Assessment (LCA). For an LCA you first want to determine the boundaries that are important to your question. Are you considering cradle to grave (disposal)? Cradle to cradle (recycling after use)? What are the boundaries for recycled source materials if used to make the light bulbs? The ...


9

I read somewhere that one issue (of several) that tends to shorten the lifetime of laptop batteries is heat from other components inside the laptop. So, if you happen to not be "on the move" with your laptop all the time, but instead end up using your laptop at the same desk for several days/weeks in a row, then you should remove the battery (don't forget to ...


9

DC motors: The most suitable motors are those which have permanent magnets in their rotors. Traditionally these were pure DC motors - where DC was fed into the motor rather than AC such as is obtained from AC mains or via a transformer, but the boundary has become blurred as a BLDC motor or BLDCM = "Brushless DC Motor" uses electronics to take supplied DC ...


9

In the purist sense of "the electricity I use was actually generated by a wind farm", your idea is broadly correct. However, unless you actually have solar panels or a wind turbine on your house, that's not how the system actually works. Broadly, all the electricity generators feed into the national grid (which in Australia covers only Qld-NSW-Vic-SA, but ...


9

Usually its around .5-10 Watts depending on the make/model/size etc. I would recommend getting a kill-a-watt meter and checking a variety of monitors to get a rough idea of the average. Then you could bring that up with regard to yearly savings. A 3 Watts average across 20 monitors per year is not nothing.


9

In Ireland, electricity is equally likely to be from renewable sources during the day as during the night ENTSO-E, the European Network of Transmission System Operators for Electricity, provides a transparency platform where you can see the hourly actual generation per production type for Ireland: It's hard to pick out a trend just by looking at a day ...


8

Your second question is the easy one: it's fine to block off one register, partly or completely. The problem comes when too many of them are blocked off (the furnace can't push enough air to work effectively). If you also have an exit vent in your room a door snake will help keep the warm air from the rest of the house out, once you've partly closed off the ...


8

You're being quite specific with regard to solar... but in principle, it is possible to move your electricity consumption to minimise its carbon footprint. Ecotricity (a UK "green" energy supplier) have a web page that shows the current carbon intensity of UK generation1, and gives a red/amber/green indication of whether you should turn stuff on now. If you ...


8

If it's a very simple motor then it may be possible just to run it backwards to generate electricity. If it's got electronic controls, probably not. But is it worth it? Do a quick calculation of the amount of energy available. How much water are you expecting to fall? (roof area x annual rainfall). One cubic metre of water weights 1000 kg. Height (metres) ...


8

Electronically they're the same and will waste as much energy as a conventional adaptor. Depending on your electrical regulations they may be forced to be at the good end of adaptor efficiency, or they may be at the very cheap end. This will be a matter of safety regulations, but the cheapest designs fall down on safety and efficiency. I hunted for one ...


8

Summary No, that's way too little. I think "140 miles square" has got mangled into "140 square miles". Running the numbers Following on from one of Elon Musk's presentations, which showed an area of about 10,000 km2 as the area of PV panels needed to power the USA, the question came up on the Skeptics Stack Exchange. Taking the numbers ...


8

The stabilisation energy rate will be exactly exactly equal to the rate at which energy is lost. Assuming the tank is closed, so there are no evaporative losses, there are two other ways energy is lost. Firstly, from conductive losses through the surface of the tank. That will depend on the thermal conductivity of the tank, and on difference between the ...


7

Here's the simplest way to do conversions like this: 180 liters * 45 degrees Celsius = 8100 kilo-calories. Google knows how to do conversions: 9.41400 kilowatt hours And it knows how to do arithmetic: 2.8242


7

Beware that chart - it is from 2004, and hence is very out of date! In particular, photovoltaics ("solar panels") have become cheaper much faster than anybody expected a decade ago, and wave and tidal power have proved more difficult and costly than some had projected. Here's some more up to date info on costs: http://www.eia.gov/forecasts/aeo/...


7

According to the REN21 Renewables Global Status Report 2014, China had 91.4 GW of installed wind capacity by the end of 2013, more than any other country in the world, of which 75.5 GW was in commercial operation. The USA had 61.6 GW of installed wind capacity. In terms of actual generation from wind, the USA was world leader in 2013, with 19.4 GW mean ...


7

The wattage given on the fixture refers to the maximum that can safely be used. That will be dictated by two things: The internal wiring of the fixture, and the heat that it can tolerate. In reality the additional 6W of the three 42W lamps that you are using is probably not going to be a problem, but it would be wrong of me to advise you that it's OK - you ...


7

I think a "general principle" is that "express wash" usually means one or more of the following reduce the wash cycle reduce the spin cycle skip a rinse cycle (e.g. by not using any softener) etc. In other words, rather than "same washing in less time" you get "less washing", but still enough for not-so-dirty clothes to get clean. This means that the ...


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